Question

Determine whether quantities vary directly or inversely and find the constant of variation.

It takes four identical water pumps 6 hours to fill a pool. How long would it take three of these same pumps to fill the pool, assuming they all pump at the same rate?

Answer 1

Time taken by 4 water pumps to fill the pool is 6 hours
Time taken by 1 pump will be:
4×6=24 hours
fraction of pool filled by a single pump in 1 hour will be:
1/24
To calculate how long it would take 3 pumps to fill the pool we proceed as follows:
Fraction of pool filled with water in 1 hour is:
3×1/24
=1/8
thus the time taken to fill the pool by 3 pumps is:
8/1=8 hours